System administrators are often tasked with managing disk usage. To do so, a system administrator may apply quotas on certain directories of various volumes of a file system. A directory upon which a quota is applied may include millions of descendants. Determining the disk space consumed by these descendants so that a quota may be enforced on the directory may take hours or days. The system administrator, however, often does not have days or even hours to wait for a quota to be applied to a directory. Furthermore, locking users and processes out of the directory while the space consumed by the directory and its descendants is computed may halt the productivity of an entire company.
What is needed is a method and system of computing the disk space used by a directory and its descendants that may proceed while input and output are occurring that involve the directory and any of its descendants.